The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A liquid crystal display (LCD) is a non-emissive display which utilizes a separate backlight unit to emit light, and red (R), green (G) and blue (B) color filters for pixels to display a color image on a screen. In some cases, the backlight is white, and each of the three color filters are absorbing other colors except for the corresponding color, which is a narrow part of the spectrum. In order to get wide color gamut, the filters have to transmit very narrow spectra. When the spectra becomes narrower, the primary colors are more saturated.
In order to improve the saturation (higher color gamut), the use of quantum dot (QD) matrix was implemented. The QD molecules are absorbing light with shorter wavelength (e.g. deep blue 450 nm) and emits, after conversion, light with a longer wavelength. Depending on the molecular physical size, the emission may be green (e.g. 550 nm) or red (e.g. 640 nm). The narrow spectra together with high quantum efficiency make the QD an attractive solution. QD materials like nano spheres (e.g. Cadmium) coated with a shell had be used, and other materials like Perovskites or phosphorous materials are also being developed.
The configuration that people are using today include blue LEDs as light source and either tubes filled with the green and red QDs near the light sources, or a films with the QDs material underneath the LCD, next to the diffusers of the backlight. A third option is to put the QDs adjacent to the blue LEDs in the same package. However, this is challenging, since the heat generated by the LED is too high for the QDs to survive.
The above solutions (QD tubes, QD films, or QD LEDs) are making a white color backlight with good gamut, after passing the color filters. Typically the gamut of the display with a backlight having white LEDs (˜72%), is increasing to 92%-NTSC or higher with the QDs. However, to generate a white color, only part of the light (about ⅓) is passing to the viewer. Thus, it will be much more efficient to put the QDs after the LCD pixels and omit the color filters. However, if the QDs are positioned away from the pixels, a leakage from a neighbor pixel can activate the QDs diagonally. A problem with this concept is the parallax issue.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.